Oral irrigators for use in the environment of a bathtub or shower stall, that include a hand-held, user-manipulatable applicator for discharging a pulsating stream of the treatment liquid, typically water, and which are driven solely by an incoming continuous-flow (i.e. non-pulsatile) stream of the liquid are known in the art. Such a device, including a turbine-incorporating adapter mounted between the water feed pipe and a conventional shower head for generating the pulsatile flow, is for example disclosed in U.S. Pat. No. 4,564,005 to Marchand.
A particularly desirable operating aspect of such oral irrigators is their ability to mix, with the pulsatile stream of water they discharge, an additive such as a medicament suitable for maintaining or enhancing the health of the teeth and/or gums of the user. In the Marchand device, this functionality is provided by including in the handpiece a cage-like compartment for holding a solid-form additive over which the pulsatile water stream is directed to melt the additive and thereby blend the additive into the discharged flow emanating from the handpiece. This manner of mixing necessarily and disadvantageously results in inconsistent and virtually unpredictable concentrations or ratios of additive to water in the resulting mixture, thereby greatly reducing, or virtually eliminating, the consistent effectiveness of the additive on the user's teeth and/or gums. Such an arrangement also significantly limits the user's ability to use a highly concentrated form of the additive--so as to correspondingly increase the period of irrigator use before which the additive in the handpiece must be replenished. The lack of real and effective control over the mixing ratio presents the possibility and risk of injury to the gums or teeth should the resulting mixture include a dangerously high concentration of the additive. Still another deficiency in the Marchand apparatus is the inability to automatically and effectively normalize or otherwise regulate and control, within predeterminately safe and consistently-maintained limits optimized for user-comfort, the pressure and volumetric flow rate of the water stream that is fed to the device from the feed source and from which the pulsatile discharge stream is generated.
An improved arrangement for dispensing a controllable ratio of an additive or medicament into a stream of treatment liquid for pulsatile discharge from an oral applicator device is disclosed in U.S. Pat. No. 4,979,503 to Chernack, commonly-owned herewith. In the Chernack irrigator, medicament in a preferably concentrated liquid form is ejected, for mixture with a pulsatile stream of the treatment liquid, from a storage reservoir by a gear pump that is directly operated by a turbine which generates the pulsatile flow from the incoming continuous-flow stream. The volume of ejected medicament concentrate for mixture with the treatment liquid is therefore directly related to, and is automatically dynamically adjusted in accordance with, the treatment liquid flow, seemingly assuring a substantially constant volumetric ratio of medicament to treatment liquid in the resulting mixture for discharge from the irrigator handpiece. In practice, however, resistance to such forced mixing of the ejected medicament and treatment liquid streams has been found to result in a variety of dynamic impediments to the attainment of a relatively constant ratio of medicament to treatment liquid in the discharged pulsatile stream.